1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
31 #include "workqueue.h"
34 #include "stringpool.h"
39 class General_options;
42 class Output_section_data;
44 class Output_section_headers;
47 class Output_data_dynamic;
50 // This task function handles mapping the input sections to output
51 // sections and laying them out in memory.
53 class Layout_task_runner : public Task_function_runner
56 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
57 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
59 Layout_task_runner(const General_options& options,
60 const Input_objects* input_objects,
63 : options_(options), input_objects_(input_objects), symtab_(symtab),
72 Layout_task_runner(const Layout_task_runner&);
73 Layout_task_runner& operator=(const Layout_task_runner&);
75 const General_options& options_;
76 const Input_objects* input_objects_;
77 Symbol_table* symtab_;
81 // This class handles the details of laying out input sections.
86 Layout(const General_options& options);
88 // Given an input section SHNDX, named NAME, with data in SHDR, from
89 // the object file OBJECT, return the output section where this
90 // input section should go. Set *OFFSET to the offset within the
92 template<int size, bool big_endian>
94 layout(Relobj *object, unsigned int shndx, const char* name,
95 const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
97 // Add an Output_section_data to the layout. This is used for
98 // special sections like the GOT section.
100 add_output_section_data(const char* name, elfcpp::Elf_Word type,
101 elfcpp::Elf_Xword flags,
102 Output_section_data*);
104 // Create dynamic sections if necessary.
106 create_initial_dynamic_sections(const Input_objects*, Symbol_table*);
108 // Define __start and __stop symbols for output sections.
110 define_section_symbols(Symbol_table*, const Target*);
112 // Return the Stringpool used for symbol names.
115 { return &this->sympool_; }
117 // Return the Stringpool used for dynamic symbol names and dynamic
121 { return &this->dynpool_; }
123 // Return whether a section is a .gnu.linkonce section, given the
126 is_linkonce(const char* name)
127 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
129 // Record the signature of a comdat section, and return whether to
130 // include it in the link. The GROUP parameter is true for a
131 // section group signature, false for a signature derived from a
132 // .gnu.linkonce section.
134 add_comdat(const char*, bool group);
136 // Finalize the layout after all the input sections have been added.
138 finalize(const Input_objects*, Symbol_table*);
140 // Return the TLS segment. This will return NULL if there isn't
144 { return this->tls_segment_; }
146 // Return the normal symbol table.
148 symtab_section() const
150 gold_assert(this->symtab_section_ != NULL);
151 return this->symtab_section_;
154 // Return the dynamic symbol table.
156 dynsym_section() const
158 gold_assert(this->dynsym_section_ != NULL);
159 return this->dynsym_section_;
162 // Return the dynamic tags.
165 { return this->dynamic_data_; }
167 // Write out data not associated with an input file or the symbol
170 write_data(const Symbol_table*, const Target*, Output_file*) const;
172 // Return an output section named NAME, or NULL if there is none.
174 find_output_section(const char* name) const;
176 // Return an output segment of type TYPE, with segment flags SET set
177 // and segment flags CLEAR clear. Return NULL if there is none.
179 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
180 elfcpp::Elf_Word clear) const;
182 // The list of segments.
184 typedef std::vector<Output_segment*> Segment_list;
186 // The list of sections not attached to a segment.
188 typedef std::vector<Output_section*> Section_list;
190 // The list of information to write out which is not attached to
191 // either a section or a segment.
192 typedef std::vector<Output_data*> Data_list;
195 Layout(const Layout&);
196 Layout& operator=(const Layout&);
198 // Mapping from .gnu.linkonce section names to output section names.
199 struct Linkonce_mapping
206 static const Linkonce_mapping linkonce_mapping[];
207 static const int linkonce_mapping_count;
209 // Handle an exception frame section.
210 template<int size, bool big_endian>
212 layout_eh_frame(Relobj*, unsigned int, const char*,
213 const elfcpp::Shdr<size, big_endian>&,
214 Output_section*, off_t*);
216 // Find the first read-only PT_LOAD segment, creating one if
219 find_first_load_seg();
221 // Create the output sections for the symbol table.
223 create_symtab_sections(int size, const Input_objects*, Symbol_table*,
226 // Create the .shstrtab section.
230 // Create the section header table.
231 Output_section_headers*
232 create_shdrs(int size, bool big_endian, off_t*);
234 // Create the dynamic symbol table.
236 create_dynamic_symtab(const Target*, Symbol_table*, Output_section** pdynstr,
237 unsigned int* plocal_dynamic_count,
238 std::vector<Symbol*>* pdynamic_symbols,
241 // Finish the .dynamic section and PT_DYNAMIC segment.
243 finish_dynamic_section(const Input_objects*, const Symbol_table*);
245 // Create the .interp section and PT_INTERP segment.
247 create_interp(const Target* target);
249 // Create the version sections.
251 create_version_sections(const Target*, const Versions*,
252 unsigned int local_symcount,
253 const std::vector<Symbol*>& dynamic_symbols,
254 const Output_section* dynstr);
256 template<int size, bool big_endian>
258 sized_create_version_sections(const Versions* versions,
259 unsigned int local_symcount,
260 const std::vector<Symbol*>& dynamic_symbols,
261 const Output_section* dynstr
264 // Return whether to include this section in the link.
265 template<int size, bool big_endian>
267 include_section(Object* object, const char* name,
268 const elfcpp::Shdr<size, big_endian>&);
270 // Return the output section name to use given an input section
271 // name. Set *PLEN to the length of the name. *PLEN must be
272 // initialized to the length of NAME.
274 output_section_name(const char* name, size_t* plen);
276 // Return the output section name to use for a linkonce section
277 // name. PLEN is as for output_section_name.
279 linkonce_output_name(const char* name, size_t* plen);
281 // Return the output section for NAME, TYPE and FLAGS.
283 get_output_section(const char* name, Stringpool::Key name_key,
284 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
286 // Create a new Output_section.
288 make_output_section(const char* name, elfcpp::Elf_Word type,
289 elfcpp::Elf_Xword flags);
291 // Set the final file offsets of all the segments.
293 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
295 // Set the final file offsets and section indexes of all the
296 // sections not associated with a segment.
298 set_section_offsets(off_t, unsigned int *pshndx);
300 // Return whether SEG1 comes before SEG2 in the output file.
302 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
304 // Map from section flags to segment flags.
305 static elfcpp::Elf_Word
306 section_flags_to_segment(elfcpp::Elf_Xword flags);
308 // A mapping used for group signatures.
309 typedef Unordered_map<std::string, bool> Signatures;
311 // Mapping from input section name/type/flags to output section. We
312 // use canonicalized strings here.
314 typedef std::pair<Stringpool::Key,
315 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
320 operator()(const Key& k) const;
323 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
325 // A comparison class for segments.
327 struct Compare_segments
330 operator()(const Output_segment* seg1, const Output_segment* seg2)
331 { return Layout::segment_precedes(seg1, seg2); }
334 // A reference to the options on the command line.
335 const General_options& options_;
336 // The output section names.
337 Stringpool namepool_;
338 // The output symbol names.
340 // The dynamic strings, if needed.
342 // The list of group sections and linkonce sections which we have seen.
343 Signatures signatures_;
344 // The mapping from input section name/type/flags to output sections.
345 Section_name_map section_name_map_;
346 // The list of output segments.
347 Segment_list segment_list_;
348 // The list of output sections.
349 Section_list section_list_;
350 // The list of output sections which are not attached to any output
352 Section_list unattached_section_list_;
353 // The list of unattached Output_data objects which require special
354 // handling because they are not Output_sections.
355 Data_list special_output_list_;
356 // A pointer to the PT_TLS segment if there is one.
357 Output_segment* tls_segment_;
358 // The SHT_SYMTAB output section.
359 Output_section* symtab_section_;
360 // The SHT_DYNSYM output section if there is one.
361 Output_section* dynsym_section_;
362 // The SHT_DYNAMIC output section if there is one.
363 Output_section* dynamic_section_;
364 // The dynamic data which goes into dynamic_section_.
365 Output_data_dynamic* dynamic_data_;
366 // The exception frame section.
367 Output_section* eh_frame_section_;
370 // This task handles writing out data which is not part of a section
373 class Write_data_task : public Task
376 Write_data_task(const Layout* layout, const Symbol_table* symtab,
377 const Target* target, Output_file* of,
378 Task_token* final_blocker)
379 : layout_(layout), symtab_(symtab), target_(target), of_(of),
380 final_blocker_(final_blocker)
383 // The standard Task methods.
386 is_runnable(Workqueue*);
395 const Layout* layout_;
396 const Symbol_table* symtab_;
397 const Target* target_;
399 Task_token* final_blocker_;
402 // This task handles writing out the global symbols.
404 class Write_symbols_task : public Task
407 Write_symbols_task(const Symbol_table* symtab, const Target* target,
408 const Stringpool* sympool, const Stringpool* dynpool,
409 Output_file* of, Task_token* final_blocker)
410 : symtab_(symtab), target_(target), sympool_(sympool), dynpool_(dynpool),
411 of_(of), final_blocker_(final_blocker)
414 // The standard Task methods.
417 is_runnable(Workqueue*);
426 const Symbol_table* symtab_;
427 const Target* target_;
428 const Stringpool* sympool_;
429 const Stringpool* dynpool_;
431 Task_token* final_blocker_;
434 // This task function handles closing the file.
436 class Close_task_runner : public Task_function_runner
439 Close_task_runner(Output_file* of)
443 // Run the operation.
451 // A small helper function to align an address.
454 align_address(uint64_t address, uint64_t addralign)
457 address = (address + addralign - 1) &~ (addralign - 1);
461 } // End namespace gold.
463 #endif // !defined(GOLD_LAYOUT_H)